The simplest way would be to upload your images to a print service that offers Holiday Cards as an option. Otherwise you'll need software like Paintshop Pro or Photoshop. There is no simple response to your question if you want to use the software.

Why not download Photo Collage Studio to have a try. Maybe it would help!

The reasons I recommend this software are
1. It's not only powerful, but also easy to use, you'll learn how to master it soon!
2. Besides greeting card, you can also use it to create photo collage, digital scrapbook, calendar and letter.
3. Offer a bundle of free templates for greeting card, photo collage and calendar.
4. Even it isn't meet your need, you needn't spend any money on it. Download the trial version, which is fully funtioned except for 30-time trial.

simple - take a [great] photo or 3, take them on a card to RITZ/Wolf Photo and print out one of their dozens of cards - we have been doing this for awhile now and it is totally easy, and cheap as heck... 2.49 each but we do 40 at a time so it costs around $20+ [we are members of their 'club' whatever it is called]. You can put whatever text you want, change font, color and size etc. It is the biggest bang for the buck.

simple - take a [great] photo or 3, take them on a card to RITZ/Wolf Photo and print out one of their dozens of cards - we have been doing this for awhile now and it is totally easy, and cheap as heck... 2.49 each but we do 40 at a time so it costs around $20+ [we are members of their 'club' whatever it is called]. You can put whatever text you want, change font, color and size etc. It is the biggest bang for the buck.